Electrochromic media for producing a preselected color

Abstract

Electrochromic compositions suitable for use in electrochromic media in electrochromic devices contain minimally two electrochromic compounds of the same redox type, whose redox potentials are greater than 30 mV. The lower redox potential electrochromic compound makes a large contribution to the absorbancy of the electrochromic medium despite being present in only minor concentration.

Description

The present invention is directed to electrochromic devices. More particularly, the present invention pertains to improved electrochromic media capable of producing a preselected color.Electrochromic devices, and electrochromic media suitable for use therein, are the subject of numerous U.S. patents, including U.S. Pat. No. 4,902,108, entitled "Single-Compartment, Self-Erasing, Solution-Phase Electrochromic Devices, Solutions for Use Therein, and Uses Thereof", issued Feb. 20, 1990 to H. J. Byker; Canadian Pat. No. 1,300,945, entitled "Automatic Rearview Mirror System for Automotive Vehicles", issued May 19, 1992 to J. H. Bechtel et al.; U.S. Pat. No. 5,128,799, entitled "Variable Reflectance Motor Vehicle Mirror", issued Jul. 7, 1992 to H. J. Byker; U.S. Pat. No. 5,202,787, entitled "Electro-Optic Device:, issued Apr. 13, 1993 to H. J. Byker et al.; U.S. Pat. No. 5,204,778, entitled "Control System For Automatic Rearview Mirrors", issued Apr. 20, 1993 to J. H. Bechtel; U.S. Pat. No...

AI Technical Summary

Benefits of technology

The net effect is that a much higher relative proportion of electroactive compounds with low redox potential are elevated to the oxidized state. For example, in a medium with only one anodic electrochromic compound, only 30% of the electrochromic compound molecules may be oxidized at any given time. In a medium with two anodic electroactive compounds of differing redox potential, of the total of the oxidized anodic species [A.sub.H.sup.+ ] and [A.sub.L.sup.+ ], perhaps 80% will be [A.sub.L.sup.+ ] species derived from the electrochromic compound of lower redox potential. Thus, electroactive components with a more easily accessible electrochemically activated state will make a more significant contribution to the absorbance spectrum of the medium than one would attribute based solely on their abundance in the medium. This enhanced contribution to the sp

Problems solved by technology

Application of voltage across the inner conductive coatings results in a change of the light reflectance of the mirror.

The colors heretofore obtainable were limited both by the stability of available electrochromic compounds as well as economic factors such as their commercial availability and expense.

Prior art electrochromic media generally employed two electrochromic compounds, one anodic and one cathodic, and were unable to acceptably produ

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